These two functions evaluate the incomplete elliptic integral of the second
kind E(φ, k) and its complete counterpart E(k)
= E(π/2, k).

The return type of these functions is computed using the result
type calculation rules when T1 and T2 are different types:
when they are the same type then the result is the same type as the arguments.

These functions are computed using only basic arithmetic operations, so
there isn't much variation in accuracy over differing platforms. Note that
only results for the widest floating point type on the system are given
as narrower types have effectively zero error.
All values are relative errors in units of epsilon.